I have done some photometry and i aim to start with a nice clean sensor window. Any other shadows may be from the filters. I don’t clean the filters and if in a filter changer, are protected somewhat.
For sensor window cleaning, I use a Delkin-Devices Digital Duster kit (They can found on e-bay). The “wand tips” are of card-like material to which a few drops of cleaner solution is added (It soaks in). The damp wand is then drawn cross the sensor slowly in one direction. The tip can be cut down to fit the sensor. Then test the camera, or if you have a eyepiece or something under a bright light, its possible to see any dust or hairs. It may be an idea to used the blower, but the danger then is that you blow material back on the window.
If you have a camera serviced in the UK (Starlight Xpress, ATik) then it may be possible to send the camera to them for cleaning. I know Starlight used to do this. Its worth asking.
This link helps to identfy the source of shadows: https://astronomy.tools/calculators/dust_reflection_calculator
